Apparatus for decomposition of metal carbonyls

ABSTRACT

Fluid bed reactors for decomposing metal carbonyls and comprising a vertically disposed, elongated vessel for confining a bed of fluidized particulate material are provided with heating coils, that can be heat exchange coils through which heating fluid is passed or electrical resistance heating coils, in the lower part of the reactor and fluidized bed so that the lower portion of the fluidized bed functions as a heating region while the upper portion functions as a decomposing zone. The lower and upper portions of the fluidized bed are volumetrically proportioned to provide substantially equal gas velocities to promote conveyance of heated particulate material from the heating region to the decomposing region. A process for decomposing metal carbonyls is also disclosed in which separate heating and decomposing regions in a fluidized bed are established and a metal carbonyl is introduced into the decomposing region via a water-cooled lance to be decomposed on heated particulate material.

United States Patent [1'91 Robinson Apr. 2, 1974 1 APPARATUS FORDECOMPOSITION OF METAL CARBONYLS Ronald Dale Robinson, Port Colbome,Ontario, Canada [75] Inventor:

[73] Assignee: The International Nickel Company,

Inc., New York, N'.(.

[22] Filed: Dec. 14, 1972 [21] Appl. No.: 315,109

Related u.s. Application Data [62] Division of Ser. No. 154,853, June21, 1971.

[52] US. Cl. l18/48, '118/DIG. 5

[51] Int. Cl. C23c 13/08 [58] Field of Search 118/4849.5,"

l18/DlG. 5, 303; 1l7/l07.l, 107.2 R, 100 R, 100 A, 100 B, 100 M, 100 C,100 D, 100 S, DIG. 6; 239/1323 [56] References Cited UNITED STATESPATENTS 2,399,717 5/1946 Aryeson 117/100 A 2,506,317 5/1950 Rex 117/100B 2,648,609 8/1953 Wurster... 117/D1G. 6 3,001,228 9/1961 Nack l17/D1G.6 3,112,274 ll/l963 Morgenthaler et al... 117/100 R UX 3,136,705 6/1964Sommers ll7/D1G. 6

3,252,823 Jacobson et a1. 117/1 17.2 R 3,566,830 3/1973 Flamm....'.118/48 3,605,685 9/1971 West et a1. 118/48 Primary Examiner-MorrisKaplan 571 ABSTRACT particulate material from the heating region to thedecomposing region. A process for decomposing metal carbonyls is alsodisclosed in which separate heating and decomposing regions in afluidized bed are established and a metal carbonyl is introduced intothe de composing region via a water-cooled lance to be decomposed onheated particulate material.

3 Claims, 2 Drawing Figures WHENTEB APR 2 I974 sum 2 BF 2 APPARATUS FORDECOMPOSITION OF METAL CARBONYLS The present application is a divisionof my application Ser. No. 154,853 filed June 21, 1971.

The present invention is particularly useful for decomposing metalcarbonyls, such as nickel tetracarbonyl or iron pentacarbonyl, and willbe described in conjunction therewith; but the present invention hasmuch wider applicability. For example, the present invention can beemployed to coat particulate material with a vaporous component bycondensing and solidifying the vaporous component on the particulatematerial.

Proposing to take advantage of the excellent gassolid contact inherentin fluidized beds, various processes for thermally decomposing metalcarbonyls in fluid bed reactors have been developed. The thermaldecomposition of metal carbonyls is an endothermic process, and theproblem most commonly encountered has been the manner in which heat issupplied to the fluid bed reactor.

Carbon monoxide, one of the products of metal carbonyl decomposition, isalso employed to dilute metal carbonyls in order that decomposition canbe more easily controlled. At temperatures below l,300F. carbon monoxideis unstable and disproportionates to carbon dioxide and elementalcarbon. The rate of carbon monoxide disproportionation is imperceptibleat room temperature but accelerates with increasing temperatures and atmetal carbonyl decomposition temperatures the rate of disproportionationis sufficiently high to cause carbon contamination problems. Thus,localized regions of high temperatures within the decomposition chambermust be avoided if carbon contamination of the carbonyl metal product isto be minimized.

It has been suggested that fluidized beds be indirectly heated bysupplying heat through the reactor walls. Although fluidized bedsprovide excellent heat transfer, particularly between the suspendedparticulate material and the fluidizing gas, it has been found that heattransfer from the reactor walls to the fluidized bed is inefficient. Ithas been postulated that a thin gaseous film or lamellar flow of gasesis created between the reactor walls and the fluidized bed and that thefilm or lamellar flow inhibits heat transfer from the reactor wall tothe fluidized bed. In some instances, measurable temperaturedifferentials of 80F. and higher have been recorded. If, during thethermal decomposition of metal carbonyls, the walls of a fluid bedreactor must be maintained at unduly high temperatures in order tosupply the requisite heat for the endothermic decomposition, thepossibility of carbon monoxide disproportionation is increased. In fact,it has been noted in the prior art that carbon associated with carbonylmetal powders produced in fluid bed reactors can be traced to the highertemperatures at the reactor walls.

In order to overcome the problems associated with inefficient heattransfer through reactor walls, it has been suggested to preheat theparticulate material to be coated and/or the fluidizing gas, e.g.,carbon monoxide. It has also been suggested that the particulatematerial be maintained in the fluidized state and at proper temperatureby employing a preheated suspension of particulate material in afluidizing gas. Merely preheating the fluidizing gas outside of thefluid bed reactor offers no guarantee that the carbonyl metal productwill be carbon free since carbon monoxide can disproportionate in thepreheater and the disproportionation products can be carried into thereactor with the same undesired result as though the disproportionationhad occurred in the fluid bed reactor. Moreover, preheating thefluidizing gas is quite inefficient because the heat capacity of gasesare volumetrically far less than the heat capacity of solids. Preheatingthe particulate material creates burdensome materials-handling problemsand requires that particulate material be continually removed from thereactor, not in response to the production rate, but wholly in responseto the heat requirements. The use of a preheated suspension ofparticulate material in the fluidizing gas to supply heat, although theexpedient works reasonably well, requires additional materials-handlingequipment and more floor space. This expedient, if not closelycontrolled, can

produce carbon via carbon monoxide disproportionation in the preheater.Although attempts were made to avoid the foregoing problems anddisadvantages, none, as far as I am aware, was entirely successful whencarried into commercial practice on an industrial scale.

It has now been discovered that metal carbonyls, including nickelcarbonyl and iron carbonyl, can be thermally decomposed in speciallydesigned fluid bed reactors while the production of carbon via thedisproportionation of carbon monoxide is minimized.

It is an object of the present invention to provide an apparatus forthermally decomposing metal carbonyls in fluid bed reactors.

Another object of the present invention is an apparatus for theproduction of carbonyl metal powders in fluid bed reactors whileminimizing carbon contamination.

Yet another object of the present invention is the provision of a fluidbed reactor especially adapted for the decomposition of metal carbonyls.

An even further object of the present invention is to provide anapparatus for controlling the heat input to a fluid bed reactor.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the drawings in which:

FIG. 1 is a longitudinal section of a fluid bed reactor in accordancewith the present invention; and

FIG. 2 is a longitudinal section of an advantageous embodiment of afluid bed reactor in accordance with the present invention that can beemployed for decomposing metal carbonyls.

Generally speaking, the present invention contemplates improved fluidbed apparatus. The fluid bed reactor comprises a vertically disposed,elongated vessel that defines a lower fluidizing zone for confining afluidized bed of particulate material and an upper particulate-materialdisengaging zone with the fluidizing zone having a lower heat exchangeregion and an upper particulate-material-treating region. The reactor isprovided with inlet and outlet means for feeding and dischargingparticulate material to and from the fluidizing zone. The reactor isalso provided with a fluidizing gas inlet for introducing fluidizing gasinto the fluidizing zone to fluidize particulate material containedtherein. Heat exchange means are located in the heat exchange region ofthe fluidizing zone to maintain particulate material in the fluidizingzone at preselected temperatures. Fluid substances for treatingparticulate material is introduced into the treating region of thefluidizing zone by fluid inlet means so that the particulate material istreated by the fluid before being discharged into the disengaging zonewithout contacting the heat exchange means.

Referring now to the drawings which are merely for the purpose ofillustrating the invention and not for limiting same, FIG. 1 is aschematic diagram of a fluid bed reactor in accordance with the presentinvention. Fluid bed reactor includes a vertically disposed elongatedvessel 12 having a conically-shaped bottom 14. Vessel l2 and its bottom14 can be made of mild steel provided that the reactants introduced intothe fluidized bed are non-corrosive and/or are not heated to unduly hightemperature. The nature of the reactants involved in the process willdictate the material out of which the vessel and other auxiliaryequipment is made. Fresh particulate material stored in hopper 18 is fedto fluidized bed 16 via rotary valve 20 and particulate material inletport 22. Treated particulate material is removed from fluidized bed 16via particulate material port 24 and valve 26 and is sent to productstorage.

The apex of conically-shaped bottom 14 of reactor 10 is provided with aventuri tube 28 that is controlled by plug-type valve 30. Fluidizing gasis introduced to reactor 10 from a blower (not shown in the drawings)through pipe 32, independently controlled valve 34 and conduit 36.

As shown in FIG. 1, fluid bed reactor 10 defines a particulate materialand gas disengaging zone A and a fluidizing zone B. Particulate materialcarried from fluidized bed 16 is disengaged from the fluidizing gas andcarbon monoxide generated by the decomposition of metal carbonyl in zoneA and drops back to fluidized bed 16. Within fluidizing zone B, whichconfines the fluidized bed 16, there is established an upperparticulate-m aterial-treating region C and a lower heatexchangingregion D. Region D can be established by mounting heat exchange coils 38in the lower portion of fluidized bed 16. Heat exchange coils 38 can beeither cooling coils or heating coils that are made of, or coated with,an abrasion-resistant material. Treating region C is that portion of thefluidized bed 16 where particulate material is treated with fluidsubstances, as described in greater detail hereinafter. Fluidsubstances, from a source not shown in the drawings, are pumped, eitherin concentrated or diluted form, by pump 40 through valve 42 intofluidized bed 16 via fluid inlet 44 and outwardly and upwardly flaringnozzle 46. Since all gaseous reagents, including the fluidizing gas andthe fluid substance, travel substantially upwardly, the fluid substancedoes not come in contact with heat exchange coils 38, and, therefore,the problems of deposition or of accretion on coils 38 heretoforeencountered are avoided. Advantageously, nozzle 44 is concentricallymounted on the vertical axis of reactor 10 or at least a sufficientdistance from the walls of the reactor to minimize accretion buildupthereon. As a further embodiment, fluid inlet 44 and nozzle 46 areconstructed to be independently temperature controlled so that the fluidsubstance can be maintained either above or below the reactiontemperature before it is discharged into fluidized bed 16.

Apparatus in accordance with the present invention is particularlyuseful for decomposing metal compounds that are heat decomposable tometal. Compounds that can be heat decomposed to metal include, althoughthe invention is not limited thereto, the carbonyls of nickel, cobaltand iron, nitrosyls or nitrosyl carbonyls of copper and cobalt, hydridesof tin and antimony, and metal alkyls, such as chromyl chloride. If areducing gas, such as hydrogen, is employed as the fluidizing gas,volatile halides of copper, nickel, cobalt and iron can also be reducedin the apparatus of the present invention. Of course, the apparatus canbe operated with cooling coils so that fluid substances can be condensedand solidified upon particulate material in fluidized bed 16 to providethe cooled particulate material with a solidified coating.

The apparatus, however, presently finds its greatest use in the thermaldecomposition of metal carbonyls, and for this purpose the apparatusdepicted in FIG. 2 is advantageously employed. Reactor 60 comprises avertically disposed, elongated cylindrical mild steel shell 62, which asshown in FIG. 2, can consist of a plurality of cylindrical sections 64having flanged ends 66. Sections 64 are assembled to provide a gas-tightchamber by placing gaskets 68 between flanges 66 before securingsections 64 with a plurality of bolts 70.

Reactor 60 is provided with a gas distribution plate 72 which can bemultiperforate to insure uniform fluidizing gas distribution (not shownin the drawings) or can be constructed to receive fluidizing tuyeres 74which function to provide uniform gas distribution while minimizingbackflow of particulate material into plenum chamber 76. Fluidizing gasis introduced into plenum chamber 76 through port 78 from a source and acompressor not shown in the drawing. Particulate material that flowsback to plenum chamber 76 is periodically removed through valved drain80.

As described hereinbefore in conjunction with FIG. 1, a disengaging zoneA and a fluidizing zone B are established in reactor 60 depicted in FIG.2. In disengaging zone A after a large proportion of entrainedparticulate material has fallen back to fluidized bed 82, spentfluidizing gas is discharged through gas outlet 84 for further treatmentto recover entrained particulate material and subsequent purificationpreparatory to being recycled to reactor 60.

When reactor 60 is employed to decompose metal carbonyls, heating regionE and decomposing region F are established within fluidized bed 82 influidizing zone B. Heating coils 85, which can beabrasionresistant-coated, hollow tubes through which heated liquids orgases are passed or electrical resistance coils that are coated with anabrasion resistant material, are fixedly mounted in region E offluidized bed 82. Metal carbonyls are introduced into the decomposingregion F through water-cooled tuyere 86. Advantageously, heating regionE and decomposing region F are volumetrically proportioned, taking intoaccount the volume displaced by heating coils 85 in heating region E, sothat the velocity of the fluidizing gas plus gases added and generatedin situ in the decomposing region F is substantially equal to thevelocity of fluidizing gas in the heating region E whereby flow ofparticulate material between these regions, and therefore heat control,is established. Seed material or particulate material to be coated isfed to fluidized bed 82 through solids port 88 from a hopper and feedvalve not shown on FIG. 2. Product, either coated powder or metalpowder, is withdrawn from fluidized bed 82 through product drain 90.

In employing the apparatus in accordance with the present invention, alower heating region and an upper treating region is established in afluidized bed of particulate material. The particulate material isheated to a preselected temperature in the heating region. A reactivevapor is introduced at a temperature below which it reacts into thetreating region whereby the reactive vapor reacts with the particulatematerial in the treating region without entering the heating region.

More specifically, when the apparatus in accordance with the presentinvention is employed for decomposing at least one metal carbonylselected from the group consisting of nickel, cobalt and iron, afluidized bed of particulate material, which can be of the metal beingdecomposed or a particulate material to be coated, is established. Aheating region is established in the lower portion of the fluidized bedto heat the particulate material to at least the metal carbonyldecomposition temperature. An upper decomposing region is establishedwithin the fluidized bed, and the metal carbonyl is introduced into thedecomposing region through a watercooled lance so that the metalcarbonyl is decomposed on the particulate material that was heated inthe heating region. When the process is conducted on a continuous basis,seed material or fresh material to be coated is continually added to thefluidized bed at a predetermined rate while product is removed from thefluidized bed at a corresponding rate. Recycle of fines for seedmaterial, as well as the rate at which material is removed from thereactor, is selected primarily to the bed depth and not in response toheat requirements.

When decomposing at least one metal carbonyl of a metal selected fromthe group consisting of nickel, cobalt and iron, a fluidized bed ofparticulate material is formed and an upper decomposing zone and a lowerheating zone are established within the fluidized bed. The particulatematerial in the decomposing region is maintained at a temperaturebetween about 300F. and 500F., advantageously 400F. to 450F., fornickel, and 400F. and 600F., advantageously 450F. and 525F., for iron.In most instances, these temperatures can be maintained by heatingparticulate material in the heating region to a temperature betweenabout 25F. and 200F., advantageously between about 50F. and l00F.,(advantageously the temperature differential for decomposing nickelcarbonyl is 50F. and about 100F. for iron pentacarbonyl) above thetemperature maintained within the decomposing region. When apparatus andprocess in accordance with the present invention are employed inconjunction with an overall process for forming a mixture of nickel andiron carbonyls, which mixture is collected in liquid iron pentacarbonyland then fractionally distilled, the metal carter-cooled lance 86, isintroduced to the decomposing region at a temperature below itsdecomposition temperature. Advantageously, the gaseous metal carbonyl isdiluted with an inert gas, such as hydrogen or carbon monoxide. lt ismost advantageous to use carbon monoxide as the diluent gas since one ofthe products of reaction is carbon monoxide and subsequent steps toremove carbon monoxide from other diluents is thereby not required. Whendiluting gaseous metal carbonyls with diluents, commercial productionrates, process control and substantially complete decomposition areobtained by using metal carbonyl concentrations in the Emmett veer;asasrrofi"giamssammm'easie meter and 2,477 grams per standard cubicmeter, advantageously, metal carbonyl concentrations as high aspossible, and even liquid metal carbonyls, are employed to provide thehighest possible production rates and to lower the risk of formingelemental carbon, particularly when decomposing iron pentacarbonyl.

For the purpose of giving those skilled in the art a better appreciationof the advantages of the invention, the following illustrative examplesare given:

EXAMPLE I A fluidized bed of 1,170 pounds of nickel particles werefluidizedby 77 standard cubic feet per minute of carbon monoxidecompressed to l4 pounds per square inch gauge and preheated to 400F. ina reactor similar to that depicted in FIG. 2 with a diameterof 14inches. A heating region was established in the lower part of thefluidizing zone by heat exchange tubes through which a heated organicfluid was passed to heat the fluidized bed to 400F. In a decomposingregion immediately above the heating region in the fluidized bed, 12standard cubic feet per minute of carbon monoxide containing 405 gramsof nickel per standard cubic meter (16 percent nickel carbonyl byvolume) was introduced into the fluidized bed through a water-cooledtuyere. During a 12 hour operating period the nickel carbonyl feed rateaveraged 22 pounds of nickel per hour, the organic fluid temperatureaveraged 471F. and the fluidized bed temperature averaged 422F. in thedecomposing region' and averaged 451F. in the heating region. Effluentgases from the fluidized bed contained 2.0 grams of nickel per standardcubic meter for a decomposition efficiency of 96.7 percent. During thetest, 200 pounds of bed were removed and 46 pouiids of minus mess mess;plus IOEouiid of impure nickel cyclone dust were added to the unit forsize control. The chemical and physical analyses of the seed and finalbed are shown in Table I:

TABLE I Tyler Particle Size, Wt, 7? Bulk Assay, 28 35 -48 -l00 200Density Ni Fe +28 +35 +48 +65 +100 +200 +325 325 lbs/ft Seed 89.9 0.81nil 0.3 0.4 0.8 33.5 60.3 3.4 1.3 Final 99.] 0.08 0.05 22.5 47.8 19.7-8.7 1.2 0.1 0.05 355 EXAMPLE II bonyls do not have t o be completelydecomposed (i.e., less than 99 percent, e.g., less than percentdecomposition) since the off-gases can be employed for fractionaldistillation if iron pentacarbonyl is incompletely decomposed orcollected in liquid iron pentacarbonyl if nickel carbonyl isincompletely decomposed. Gaseous metal carbonyl, advantageously fedthrough a waestablished with 995 pounds of particulate sponge iron whichwas fluidized with 40 standard cubic feet per minute of carbon monoxidecompressed to l3 pounds per square inch gauge and preheated to 347F. Thefluidized bed was heated to 500F. in the heating region within thefluidized bed prior to admittin g 27.3 standard cubic feet per minute ofcarbon monoxide containing 120 grams nickel per standard cubic meter (5percent nickel carbonyl by volume) and 355 grants iron per standardcubic meter percent iron pentacarbonyl by volume) through a water-cooledtuyere. During the operating period of 3% hours the feed rate averaged56 pounds of nickel plus iron per hour, the temperature of the heatingregion averaged 590F. and the temperature of the decomposing regionaveraged 519F. The effluent gases exiting from the fluidized bedcontained 0.31 grams iron per standard cubic meter and 0.05 grams nickelper standard cubic meter for de-' Although the present invention hasbeen described in conjunction with preferred embodiments, it is to beunderstood that modifications and variations may be resorted to withoutdeparting from the spirit and scope of the invention, as those skilledin the art will readily understand. Such modifications and variationsare considered to be within the purview and scope of the invention andappended claims.

I claim:

1. A fluid bed reactor for decomposing metal carbonyls which comprises avertically disposed, elongated vessel that defines a lower fluidizingzone for confining a fluidized bed of particulate material and an upperparticulate material and gas disengaging zone with the fluidizing zonehaving a lower heating region and an upper decomposing region, a plenumcharacter having a multiperforate plate common with the bottom of theheating region of the fluidizing zone and through which fluidizing gasis introduced into said zone for fluidizing the particulate materialcontained therein, inlet and outlet means for feeding and dischargingparticulate EXAMPLE "I This example confirms that iron pentacarbonyl canbe decomposed in a fluid bed reactor similar to that depicted in FIG. 2.The reactor had an internal diameter of 5 inches and was provided withelectrical resistance heaters. 7 7

A fluidized bed of 1 10 pounds of ferronickel plated sponge iron,prepared as described in Example Il, was fluidized by 6.1 standard cubicfeet per minute of carbon monoxide. The fluidized bed was heated to400F. by the electrical resistance heating elements prior to admitting8.3 standard cubic feet per minute of carbon monoxide containing 152grams iron per standard cubic meter (6.4 percent) iron pentacarbonyl byvolume) through a water-cooled tuyere. During an operating period of 48hours, the feed rate averaged 5 pounds of iron per hour and thedecomposing region of the fluidized bed averaged 440F. The effluentgases contained 6.3 grams iron per standard cubic meter fordecomposition efficiencies of 92 percent. During the test, 294 pounds ofproduct were removed and 126 pounds of minus 65 mesh fraction plus 22pounds of sponge iron seed were added to the unit for size control. Theplated iron contained l.8 percent carbon on an overall balance. Thechemical and physical analyses of the seed, final bed and product areshown in Table lll.

material to and from the fluidizing zone, a fluidizing gas inlet forintroducing fluidizing gas into the plenum chamber, heat exchange meansmounted in the heating region to heat particulate material to thedecomposition temperature of the metal carbonyl, a vertically disposedwater cooled lance passing centrally through the heating zone anddischarging into the lower end of the decomposition region forintroducing metal carbonyl into the decomposing region so that metalcarbonyl is decomposed on heated particulate material, generating carbonmonoxide, the heating region and the decomposing region of thefluidizing zone being volumetrically proportioned so that the velocityof the fluidizing gas in the heating region is substantially equal tothe velocity of the fluidizing gas plus the generated carbon monoxide inthe decomposing region whereby conveyance of particulate materialbetween the heating region and the decomposing region is promoted.

2. The fluid bed reactor as described in claim 1 wherein the heatexchange means is a hollow tube through which heated fluid is passed toheat particulate material in the heating region.

3. The fluid bed reactor as described in claim 1 wherein the heatingmeans is an electrical resistance heater for heating particulatematerial in the heating region.

TABLE III 7 Tyler Particle Size, Wt, Bulk Assay, 71 28 -35 48 l00 -200Density Ni C +28 +35 +48 +65 +200 +325 325 lbs/ft" Seed ().I4 ().I l 0.144.4 40.7 14.0 0.4 0.4 202 Final L76 1.65 0.2 4.9 26.5 57.7 10.1 0.6 3l7Bed Product 2.44 1.73 0.4 3.9 35.2 55.5 4.8 0.2 309

2. The fluid bed reactor as described in claim 1 wherein the heatexchange means is a hollow tube through which heated fluid is passed toheat particulate material in the heating region.
 3. The fluid bedreactor as described in claim 1 wherein the heating means is anelectrical resistance heater for heating particulate material in theheating region.